1. Field of the Invention
The present invention relates to a pressure sensor assemblage that can be used in particular in motor vehicles.
2. Description of the Related Art
Pressure sensors can be used to measure gas pressures in systems. For example, a gas pressure inside a gas-conveying or gas-containing system can be measured, absolutely or relative to a reference pressure, with the aid of a pressure sensor. Alternatively, two gas pressures can be measured relative to one another, for example at different locations in a gas-conveying or gas-containing system. In the latter case the term “differential pressure sensor” is also used.
Pressure sensor assemblages are used in motor vehicles, inter alia, in order to sense an absolute intake manifold pressure in Otto-cycle or turbodiesel engines. Such pressure sensor assemblages are also referred to as “manifold absolute pressure” (MAP) sensors. Alternatively, for example, a differential pressure assemblage can be used in a motor vehicle in order to identify a degree of contamination in a diesel particle filter, based on a gas pressure existing in an inflow to the filter relative to a gas pressure existing in an outflow.
Pressure sensors nowadays are usually implemented as micromechanical components, and generally have a detection surface that is designed to modify its physical properties as a function of pressures acting on it. The detection surface can be implemented, for example, as a thin membrane that deforms upon the impingement of pressure. Changes in physical parameters which occur as a result of the deformation can be measured, for example, by way of an integrated circuit, and then outputted as a signal that carries information regarding the prevailing gas pressure.
European Patent EP 1 521 952 B1 describes an apparatus for pressure measurement that is suitable for pressure measurement, in particular for differential pressure measurement, in motor vehicles.
In order for the detection surface of the pressure sensor to be able to sense the pressure, requiring measurement, of a gas in a system, a gas-permeable connection should exist between the system and a volume adjacent to the detection surface. A change in pressure in the system can then, by gas exchange, bring about a modified pressure on the detection surface.
Penetration of substances into a housing surrounding the micromechanical pressure sensor can, however, also occur through the gas-permeable connection. In particular, substances that can damage the pressure sensor can be contained in the gas whose pressure is to be measured.
It has been observed, for example, that iodine or iodide that arrives at the pressure sensor can, for example, damage contacts there. Iodine or iodide can, for example, be released over time from the material of supply conduits that lead to the pressure sensor assemblage.
Efforts have previously been made to protect the components that are sensitive to penetrating damaging substances, for example, with a cover layer made of less-sensitive material such as gold.
In an alternative approach to a solution, so-called “sacrificial” structures are used; these bind by chemical reactions to the potentially damaging substances that penetrate, but are themselves consumed in the process. Sacrificial structures made of loose silver wool or silver wire, for example, can be used to bind penetrating iodine.